Understanding Proportions through Cross Multiplication

Front

What is a proportion?

Back

A proportion is an equation that states that two ratios are equal.

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CCSS.7.RP.A.2A

Front

How do you solve for a variable in a proportion?

Back

You can solve for a variable in a proportion by cross multiplying.

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CCSS.7.RP.A.2C

Front

What does cross multiplication involve?

Back

Cross multiplication involves multiplying the numerator of one ratio by the denominator of the other ratio.

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CCSS.6.RP.A.3A

Front

If 4/10 = N/25, what is the first step to solve for N?

Back

Cross multiply to get 4 * 25 = 10 * N.

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CCSS.7.RP.A.3

Front

What is the result of cross multiplying 4/10 and N/25?

Back

100 = 10N.

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CCSS.5.NF.B.5B

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How do you isolate the variable N in the equation 100 = 10N?

Back

Divide both sides by 10 to get N = 10.

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CCSS.6.EE.B.7

Front

What does the equation 9M = 72 tell us about M?

Back

M is exactly 8, since 72 divided by 9 equals 8.

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CCSS.3.OA.B.6

Front

What is the first step in solving the equation 20X = 120?

Back

Divide both sides by 20 to find X.

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CCSS.6.EE.B.7

Front

What is the value of X in the equation 20X = 120?

Back

X is 6, since 120 divided by 20 equals 6.

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CCSS.3.OA.B.6

Front

What is the purpose of cross multiplication in solving proportions?

Back

Cross multiplication helps to eliminate the fractions and simplify the equation.